Problem: trim(): hard to use default mask
Solution: Use default 'mask' when it is v:none
The default 'mask' value is pretty complex, as it includes many
characters. Yet, if one needs to specify the trimming direction, the
third argument, 'trim()' currently requires the 'mask' value to be
provided explicitly.
'v:none' is already used to mean "use the default argument value" in
user defined functions. See |none-function_argument| in help.
closes: #13363
Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Illia Bobyr <illia.bobyr@gmail.com>